#include "csapp.h"
int main(int argc, char **argv) 
{
char **pp;
struct in_addr addr;
struct hostent *hostp;
if (argc != 2) {
fprintf(stderr, "usage: %s <domain name or dotted-decimal>\n", 
argv[0]);
exit(0);
}
if (inet_aton(argv[1], &addr) != 0) 
hostp = Gethostbyaddr((const char *)&addr, sizeof(addr), AF_INET); 
else                                
hostp = Gethostbyname(argv[1]);
printf("official hostname: %s\n", hostp->h_name);
for (pp = hostp->h_aliases; *pp != NULL; pp++)
printf("alias: %s\n", *pp);
for (pp = hostp->h_addr_list; *pp != NULL; pp++) {
addr.s_addr = ((struct in_addr *)*pp)->s_addr;
printf("address: %s\n", inet_ntoa(addr));
}
exit(0);
}
